LEDs are widely used in short haul fiber optic systems because they are relatively inexpensive, however, they are limited to lower speed applications, e.g. a top bandwidth of 100–300 MHz. The three main types of laser diodes used in fiber optic systems are the Fabry-Perot (FP) laser diode, the distributed feedback (DFB) laser diode and the vertical cavity surface emitting laser (VCSEL). The three main types of detectors that are used in fiber optic systems are PIN photo diodes, integrated detector/pre-amplifiers (IDPs), and avalanche photo-diodes (APDs), with PIN photo diodes being the most commonly used detector.
FIG. 1 illustrates a conventional parallel fiber optic interconnect arrangement 10 that employs an edge emitter approach. It comprises a 1×4 array 12 of edge emitting laser diodes attached to a ceramic submount 14 and positioned opposite four facets of a 1×4 array 16 of optical fibers. The ceramic submount 14 is supported on a silicon block 18. Alignment within five microns is typically required along both the X and Y axes. The optical fibers 16 sit side-by-side within upwardly opening V-shaped grooves 20 etched in the upper surface of another silicon support block 22. The height of block 22, the placement of the V-shaped grooves 20 relative to block 22, and the optical fibers 16 in them is generally very precise. What is generally not as precise is the gap between submount 14 and silicon block 18, and between the silicon block 18 and the grooves 20, and the package (not pictured) below. In order to align in two axes, either the parts need to be made to high precision, which is costly, or aligned in multiple axes, either actively (device on) or passively (using fiducials), which is also costly.